Parametric assessment of electrical discharge drilling on plasma sprayed functionally graded Al/Al2O3 coating on Al6061-T6 faceplates

Abstract

Electrical discharge drilling is a non-conventional machining process that is effective and economical for cutting difficult-to-cut conductive materials. In this work, the parametric assessment of functionally graded Al/Al2O3 coating sprayed by plasma on Al6061-T6 faceplates is investigated. Initially, four different graded layers of Al/Al2O3 (50:50, 40:60, 30:70, and 20:80) were processed through plasma spray and deposited coating morphology, splat formation, and cross-sectional structure were confirmed through a scanning electron microscope. The parametric assessment has been investigated based on the effect of electrical discharge drilling parameters peak current (Pc), pulse-on time (Pon), and gap voltage (Vg) on the material removal rate (MRR), tool wear rate (TWR), machining time (MT), surface roughness (SR), taper angle (TA), and overcut (OC). The selected process parameters were Pc from 8 to 14 A, Pon from 60 to 90 μs, and Vg from 20 to 80 V respectively. The parametric assessment was performed based on the objectives of maximizing the MRR and minimizing the TWR, MT, SR, TA, and OC. The effect of process parameters on various output responses was summarized. From the experimentation, MRR is significantly affected by Vg, and maximum MRR is found at the high levels of Pc and Pon. Reduced TWR was observed at the 2nd level of Pc (0.058 mm3 min−1) and 4th level of Vg (0.076 mm3 min−1) and this same factor has more influence on MT. High level of Pc and Pon exhibits maximum TWR with erosion. The results show that Pon time relatively gives low SR (2.36 μm) and minimum OC (0.0015 mm) was achieved at a high level of Vg. Few un-drilled holes with cracks were witnessed due to high TWR. Many drilled holes exhibit < 2° of TA which indicates good dimensional accuracy.